1. Field of the Invention
The present invention relates to a vehicle frame having an independent seat frame. More particularly, the invention relates to a motorized go cart racing frame with an independent seat frame mounted thereon to concentrate the weight of a driver at selected locations of the racing frame.
2. Description of the Prior Art
The sport of go cart racing typically involves a plurality of motorized go carts racing one or more times around a track, with the object being to cross a predetermined finish line ahead of the other go carts. Go cart race tracks are traditionally oval in shape, and the go carts race in a counterclockwise direction. On an oval track, therefore, the go carts must continuously negotiate tight left hand corners. Race tracks in shapes other than ovals are also used for racing, but these tracks are usually designed to have left hand turns while having usually wider right hand turns. The surface of the racing tracks can vary and can be made of, for example, dirt, clay or asphalt. In addition, many tracks use banked curves to allow the go carts to travel at higher speeds. The racing speeds of the motorized go carts can reach over 100 mph.
The basic components of a go cart are well known in the art. A conventional go cart frame 10 is shown in FIG. 1 and is typically comprised of 1'1/8 thin-wall tubing welded together at all joints. Two extended frame members 12 and 14 form the sides (right and left, respectively, from the driver's perspective) of the vehicle frame, or chassis. The extended frame members are weld-connected together by front, middle and rear transverse frame members 16, 18 and 20, respectively. A flat bar 21 is secured between the extended frame members to support a floor board (unshown). The motor 22 is usually mounted on the right rear portion of the chassis for reasons that will be discussed below. The chassis shown in FIG. 1 includes a motor-supporting member 24 and brackets 26 for helping to support the motor.
A seat 28 is rigidly secured to middle transverse frame member 18 and includes adjustable rear and side seat supports 30 and 32 attached to the chassis. The supports are adjusted to balance the weight of the go cart and the driver to achieve approximately equal weight distribution on the left and right sides of the chassis. Seat 28 in FIG. 1 is also positioned slightly left of center to offset the weight of the motor on the right side. The go cart is conventionally designed to have approximately 40% of the weight supported on front wheels 27 and approximately 60% of the weight supported on rear wheels 29.
Since go cart racing tracks are configured to have predominantly left hand turns, an ongoing objective is to design go carts which can negotiate left hand turns at higher and higher speeds. This objective is particularly challenging because go carts use a live rear axle. The live axle rotates both rear wheels at the same speed at all times. The live axle is distinguished from the more expensive differential axle, which uses a gear box to vary the rotational speeds of the rear wheels when the vehicle is turning and to reduce the rotational speed (and thus the driving force) on the inside wheel. Having a live axle makes cornering in either direction difficult because, at the high speeds travelled by the go cart, the rear wheels provide a significant driving force in the straight ahead direction. It is well known that the cornering ability of the go cart is improved when the driving force provided by the rear wheel on the side of the turn (i.e. the inside rear wheel) is reduced.
When the go cart enters a left hand turn, centrifugal force shifts the weight (particularly the upper body weight) of the driver to the right side of the cart. The weight shift in the rear of the cart is desirable because it puts extra weight on the right rear wheel (improving traction) while removing weight from the left rear wheel (reducing traction). The motor is usually mounted on the right side of the go cart to provide additional weight on the right rear wheel. If enough weight is lifted off the left rear wheel, it will lose traction completely and spin, enabling the right rear wheel alone to propel the go cart around the corner. However, because the seat is rigidly mounted to the chassis, the effect of the driver's weight shift normally is relatively small and there is little or no traction loss by the left rear wheel.
The weight shift of the driver when making a left turn also shifts weight from the left front wheel to the right front wheel. Since the front wheels do not support as much weight as the rear wheels, this weight shift from the left front wheel causes it to lose traction, thus reducing its ability to help steer the go cart. With only one front wheel (right) in solid contact with the surface of the track, cornering is made more difficult.
Recognizing that if two objectives can be accomplished a go cart with better left hand cornering ability can be achieved, at least one solution has been proposed in the prior art. The first objective is to design the go cart so that the right rear wheel provides a significantly greater driving force than the left rear wheel. The second objective is to design the go cart so that the left front wheel compensates for the weight shift to the right front wheel and provides at least some assistance in steering the go cart through a left turn.
The prior art solution is to provide a "stagger" adjustment to the go cart. The stagger adjustment attempts to add more weight to the left front wheel and the right rear wheel. One way to accomplish this is to use larger diameter tires at the left front position and the right rear position than in the other two tire positions. The larger tire has increased weight, which adds to the weight gain in the right rear portion of the chassis and compensates for the weight loss in the left front portion of the chassis. In addition, because the bigger tires have a larger circumference, the right rear wheel travels further than the left rear wheel on a single rotation, thus tending to turn the cart left at all times. Also, a larger circumference places more surface area of the left front tire into contact with the track than the right front tire, thus improving traction at the left front wheel. Another alternative that has been used is to simply increase the air pressure in the left front and right rear wheels. This tends to provide the same effect as using tires of increased diameters.
Using such a "stagger" adjustment works to some degree in helping the go cart to make high speed left hand turns. However, the conventional stagger adjustment has a serious drawback, in that the increased weight and/or diameter at the left front wheel and right rear wheel is a permanent adjustment. This has an adverse effect on steering the go cart on straight portions of the track (and when making right turns) because it tends to pull the cart to the left.
Accordingly, further advantages and improvements in go cart racing frames are needed.